The invention relates to a mercury-vapor discharge lamp for a homogeneous, planar irradiation, having a lamp bulb made of quartz glass, which encloses a closed discharge space into which two electrodes project, with a non-linear gas discharge channel extending between these electrodes.
UV emitters, such as mercury-vapor discharge lamps, are used, for example, for purifying or modifying the surfaces of substrates, or for the sterilization or activation of surfaces. Typically, processing is performed here with UV light in the wavelength range of 160 to 400 nm.
For a high productivity production line, a high UV light intensity is required in the area of the surface to be processed. The homogeneity of the UV irradiation is often of decisive importance for the irradiation result, especially for applications in which the surface to be irradiated is not moved relative to the UV emitter.
For a high UV light intensity, a smallest possible distance between the surface and UV emitter is advantageous. On the other hand, a small distance makes homogeneous illumination more difficult, because the UV radiation intensity is inhomogeneous in the near field of the emitter.
For generating a planar irradiation, UV emitters are known, for example, from German published patent application DE 34 37 212 A1 and German utility model DE 91 08 294 U1, in which the lamp bulb is bent into a U shape or meander shape or is assembled from tube parts which as a whole have a U-shaped or meander-shaped profile.
A lamp bulb folded into a meander shape, however, cannot be easily folded without interruption, so that gaps are created between the legs of the meander, which negatively affect the homogeneity of the light distribution.
In an alternative embodiment, in which several elongated UV emitters are arranged parallel to each other and in a common plane, an essentially homogeneous radiation field can indeed be achieved. However, such emitter arrangements are associated with high assembly and adjustment expense, and the multitude of lamps and ballasts also require high structural expense. In addition, upon failure of only a single emitter, often the entire emitter set must be exchanged, in order to avoid inhomogeneities due to different aging processes of the emitters.